A conventional optical pick-up (OPU) apparatus enables information to be recorded, reproduced and erased with respect to a CD group disc (e.g. CD, CD-ROM, CD-R and CD-RW) and a DVD group disc (e.g. DVD, DVD-ROM, DVD-RAM, DVD-R and DVD-RW, DVD+R, DVD+RW), as well as to write/read more recently introduced Blu-ray discs and/or HD-DVD format discs, with single or multiple layer formats. As known in the art, the OPU generally has an infrared semiconductor laser device for CD (about 780 nm), and a red semiconductor laser device for DVD (about 650 nm) and/or a blue laser device for Blu-ray/HD-DVD (about 405 nm). The OPU includes photo detector IC (PDIC), and power monitor integrated circuit (PMIC), which both generally provide a fixed detection pattern.
In typical applications, each laser beam, such as infrared (780 nm for CD), red for DVD (about 650 nm) and blue (405 nm for Blu-ray and HD-DVD) is split to 3 beams by optical gratings, forming a central beam (zero order) and two side beams (first order). The center beam reads the disc data, while the side beams help to keep the beam in the disc track.
One problem during development of PDICs and PMICs for optical pickup units (OPUs) relates to the need to select a photo detector detection pattern before testing the system, since available photo detectors provide a fixed detection pattern and modeling is not currently possible. Unfortunately, testing may reveal a fixed pattern initially specified does not provide the desired detector performance.
For example, one issue for the optical storage industry is related to the unpredictable introduction of interference patterns on the servo tracking signal caused by unwanted optical reflections when reading dual layer Blu-ray media. This issue can require a redesign of the photo detector patterns on the PDIC, thus leading to a time an expensive, time consuming and highly iterative design process.